dihydropyridines and Myocarditis

The aim of the present study was to compare the cardioprotective properties of long-acting calcium channel antagonist pranidipine with amlodipine in rat model of heart failure induced by autoimmune myocarditis. Twenty-eight days after immunization the surviving rats were randomized for the oral administration of low-dose amlodipine (1 mg/kg/day), high-dose amlodipine (5 mg/kg/day), pranidipine (0.3 mg/kg/day) or vehicle (0.5% methylcellulose). After oral administration for 1 month, the animals underwent echocardiography and hemodynamic analysis. Histopathology, immunohistochemistry, and Western immunoblotting were carried out in the heart samples. Both pranidipine and high-dose amlodipine increased survival rate. Although the heart rate did not differ among the four groups, left ventricular end-diastolic pressure was significantly decreased and +/-dP/dt was increased in the pranidipine- and high-dose amlodipine-treated rats, but not in low-dose amlodipine-treated rats. In comparison to amlodipine treatment, pranidipine treatment significantly reduced myocyte size and central venous pressure. Furthermore, both pranidipine and high-dose amlodipine treatment significantly reduced myocardial protein levels of atrial natriuretic peptide and inducible nitric oxide synthase, whereas pranidipine only significantly decreased tumor necrosis factor-alpha, and improved sarcoplasmic reticulum Ca2+ ATPase2 protein levels. We conclude that pranidipine ameliorates the progression of left ventricular dysfunction and cardiac remodeling in rats with heart failure after autoimmune myocarditis in a lower dose when compared to amlodipine and which may be a clinically potential therapeutic agent for the treatment of heart failure.

Topics: Administration, Oral; Amlodipine; Animals; Atrial Natriuretic Factor; Blood Pressure; Calcium Channel Blockers; Calcium-Transporting ATPases; Cardiac Myosins; Dihydropyridines; Dose-Response Relationship, Drug; Echocardiography; Fibrosis; Heart Failure; Heart Rate; Male; Myocarditis; Myocardium; Nitric Oxide Synthase Type II; Rats; Rats, Inbred Lew; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Survival Rate; Time Factors; Ventricular Function, Left

The cardioprotective properties of pranidipine were studied in a rat model of heart failure after autoimmune myocarditis. Twenty-eight days after immunization the surviving rats were divided into three groups and received oral treatment of 0.03 mg/kg/day (group 0.03) or 0.3 mg/kg/day (group 0.3) of pranidipine or vehicle (group V) for 1 month. High-dose pranidipine (group 0.3) improved the survival rate, and significantly reduced heart weight, heart weight to body weight ratio, myocardial fibrosis, central venous pressure and left ventricular end-diastolic pressure than low-dose pranidipine (group 0.03) and group V. Pranidipine at high dose also decreased the left ventricular systolic and diastolic dimensions, and increased fractional shortening compared with group V. The increase in level of TGF-beta1 and collagen-III mRNA were suppressed by pranidipine in a dose-dependent manner. Our results indicated that pranidipine has cardioprotective effects on heart failure, and that the beneficial effect can be partly explained by attenuation of fibrotic response through suppression of TGF-beta1 and collagen-III mRNA expression, and regression of myocyte hypertrophy.

Topics: Animals; Blood Pressure; Calcium Channel Blockers; Dihydropyridines; Heart Failure; Heart Rate; Male; Myocarditis; Rats; Rats, Inbred Lew; Transforming Growth Factor beta; Ventricular Dysfunction, Left; Ventricular Remodeling

Excessive production of nitric oxide (NO) by inducible NO synthase (iNOS) contributes to the progression of myocardial damage in myocarditis. Some dihydropyridine calcium channel blockers reportedly inhibit NO production and proinflammatory cytokines and the present study sought to clarify if a low dose of benidipine, a novel dihydropyridine calcium channel blocker, would ameliorate experimental autoimmune myocarditis (EAM). Rats with or without myocarditis were administered oral benidipine at a dose of 3 mg. kg(-1). day(-1) for 3 weeks. Low-dose benidipine did not decrease blood pressure significantly compared with the untreated group, but markedly reduced the severity of myocarditis. Myocardial interleukin-1beta (IL-1beta) expression and IL-1beta-positive cells were significantly less in rats with EAM that were treated with low-dose benidipine compared with untreated rats. Also, myocardial iNOS expression and iNOS-positive cells were markedly reduced in in the treated rats compared with the untreated group. Furthermore, myocardial NO production and nitrotyrosine expression were suppressed by the treatment in rats with EAM. The cardioprotection of low-dose benidipine may be caused by suppression of inflammatory cytokines and inhibition of NO production.

Topics: Acute Disease; Animals; Autoimmune Diseases; Blood Pressure; Calcium Channel Blockers; Calcium Channels, L-Type; Cytokines; Dihydropyridines; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Heart Rate; Myocarditis; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Peroxynitrous Acid; Rats; Rats, Inbred Lew; Tyrosine

ICI 153,110 is an inotropic vasodilator compound intended for the treatment of congestive heart failure. It was administered to rats at dose levels of 5, 10, and 250 mg/kg/day for up to 6 months as part of its preclinical development program. Detailed clinical investigations were conducted during the course of the study and histopathological examination took place after 28 days and 182 days of treatment as well as 42 days following cessation of dosing. Changes were identified in blood vessels in the greater proportion of animals from the high dose group, although some of the changes were also observed at lower dose levels. Vascular tissues from a variety of sites were affected, particularly those of the mesentery, splanchnum, heart, testis, and the pampiniform plexus. Early changes characteristic of acute injury such as arterial medial necrosis and inflammation occurred, which were distinguishable from those following chronic administration of the compound where there was a pronounced arterial and venous wall thickening and accompanying plexiform vasculopathy. The essential components contributing to the thickening were a smooth muscle hypertrophy and hyperplasia of the media. At the end of the period following withdrawal of dosing, vascular thickening was still present and arteritis showed an increased incidence relative to that seen at termination of the main test. Systemic hypertension was not detected during these studies. Vasodilation occurring at or near normal blood pressure, resulting in breakdown of vascular autoregulation and excessive critical wall tension, may have been the cause of the pathological changes. Our findings indicate that medial necrosis is an early component in a sequence of adaptive, destructive, and reparative changes not only following a chemically induced perturbation of the hemodynamic status in arteries and veins but also following a shift back to the "normal state" on withdrawal of compound.

Topics: Animals; Aorta; Arteritis; Blood Pressure; Blood Vessels; Body Temperature; Cardiotonic Agents; Dihydropyridines; Dose-Response Relationship, Drug; Endomyocardial Fibrosis; Female; Heart Rate; Hyperplasia; Hypertrophy; Male; Mesenteric Veins; Mesentery; Muscle, Smooth, Vascular; Myocarditis; Myocardium; Pericarditis; Pyridazines; Random Allocation; Rats; Time Factors; Vasodilator Agents